This invention is directed to methods for the manufacture and repair of dental appliances especially crowns and bridges. More particularly, a system is provided whereby dental appliances may be fabricated or repaired in the mouth or externally. Such methods are provided which provide dental appliances which are physically and aesthetically superior to those presently known. In addition, this invention is directed to materials useful for the preparation of dental appliances and for the repair thereof which have the ability to bond to metallic underlayments or substrates with improved tenacity.
The fracture of porcelain from fixed dental appliances such as crowns and bridge work has been a problem for dentists for many years. The repair of such prostheses has been accomplished in the past in two ways. Typically, a prostheses is removed from the patient's mouth and repaired in a dental laboratory. This procedure may be quite painful and traumatic to the patient. Further, damage to existing dentition and/or to the dental appliance itself is frequently encountered. This procedure requires extensive amounts of practitioner time in the mouth with attendant expense. In the alternative, it has been known to repair dental appliances while they remain fixed within a patient's mouth. While this effects a substantial savings in working time in the mouth, prior methods and materials have provided only mediocre aesthetic results having a relatively short lifetime.
It will be appreciated that the construction and repair of dental appliances necessarily involve the bonding of materials to dental metals. Such prosthetic devices generally comprise shaped metallic underlayments which are fabricated from a metallic species or alloy having good strength, durability, etc. and also compatability with the oral environment. Such alloys, which frequently include high gold alloys, are generally inert and provide a difficult bonding surface. Accordingly, prior art materials and methods which involve the application of polymerizable adhesives and other materials to the surface of dental alloys have had poor bond strengths and concomitant poor durabilities. Efforts to overcome these shortcomings have not been successful. For example, a cold-setting ethoxylated bisphenol-A dimethacrylate resin sold by the Denmat Company incorporates certain silanous materials such as .gamma.-methacryloxypropyltrimethoxysilane and other materials as adhesion promoters for application to dental metals. Such material does not provide permanent bonding to dental alloys, however. Fusion.TM. is a two component material, (believed to be a silane-based product) which has been sold as an adhesion promoter. Metalit.TM. is a cyanoacrylate based system which, again, is believed to provide only a temporary bond to dental alloys in the oral environment. It is believed that when applied to dental alloys, the foregoing materials bond only weakly to the metal. It is further believed that oral fluids are capable of hydrolyzing or otherwise destroying this bonding causing a loss of adhesion to the metal underlayment or substrate.
U.S. Pat. No. 3,889,385 issued to Dougherty discloses dental opaqueing materials comprising copolymers of methyl methacrylate and acrylonitrile in a solvent medium. Small amounts of acrylic or methacrylic acid may be included in these compositions as may certain silanes.
U.S. Pat. No. 3,997,637 issued to Rogers discloses methods for making tooth reconstructions employing electrodeposition techniques. U.S. Pat. No. 4,125,442 also to Rogers discloses the preparation of composite tooth reconstructions by bonding porcelain over a basis metal coated with electrolytically deposited metal to improve the bond strength of the porcelain to the metal.
U.S. Pat. No. 4,247,575 issued to O'Connell et al is directed to methods for electroless plating of silver onto tooth structures, especially dentin.
U.S. Pat. No. 4,295,951 to Lustgarten provides improved porcelain coated metal dental articles through electroplating gold over a non-precious metal substrate, adding finely divided gold particles thereto and firing porcelainic materials thereover.
McLean in "Aesthetics and Restorative Dentistry: The Challenge for the Future" British Dent. Journal Vol. 149, pp. 368 et. seq. (1980) suggests the coating of nickel-chrome with noble metals such as gold, platinum or rhodium by electroplating followed by plating to improve the receptivity of the metal to porcelain coatings.
None of the foregoing discloses or suggests the novel methods and materials of the present invention.